post https://api.intersoftsapient.net/v4/shipments/preallocateTrackingNumber/rm
This service can be used to receive a Royal Mail Tracking Number that will be pre-allocated to the service and destination supplied in the request. No shipment or label will be produced from this service.
This service can only be used for services that are assigned a tracking number.
This service must be used in conjunction with CreateShipment service populating the TrackingNumber in the CarrierSpecifics /PreAllocatedBarcode section with the pre-allocated TrackingNumber returned in this service response.